Evolution of immunotherapy in the treatment of non-muscle-invasive bladder cancer

Introduction: Immunotherapy with intravesical bacillus Calmette–Guérin (BCG) has been the gold standard treatment for intermediate- and high-risk non-muscle-invasive bladder cancer (NMIBC) for nearly half a century. Yet, many patients with high-risk disease will experience recurrence, including those who progress and eventually become unresponsive to BCG. For decades, apart from radical cystectomy, few therapeutic options existed for this at-risk population. However, the advent of novel immunotherapeutic agents has transformed treatment in a range of tumor types, including urothelial carcinoma. These immunotherapies have yielded promising results in the treatment of metastatic urothelial carcinoma and, as such, are also being investigated for use in NIMIBC. Areas covered: This article provides an overview of the evolution of immunotherapy for NMIBC, beginning from the original immunotherapy-BCG–to current agents including checkpoint inhibitors, IL-15 agonists, viral gene therapies and therapeutic cancer vaccines. Expert opinion: Emerging insights over the last decade have led to the development of novel immunotherapiesfor the treatment of NMIBC whilst providing new opportunities to enhance the anti-tumour activity of BCG. In particular, the KEYNOTE-057 trial represents a pivotal moment for immunotherapy in NMIBC, leading to approval of pembrolizumab by the US Food & Drug Administration for patients with BCG-unresponsive disease. However, patient selection and the development of biomarkers to guide the identification of patients who will benefit most from a particular immunotherapy remains critical. As research efforts come to fruition, these novel immunotherapies may become integrated into the standard treatment paradigm for intermediate- and high-risk NMBIC.